'The Sing Off' at NBC finished fourth-place Monday

From 8-10 p.m. ET, a holiday edition of “The Sing-Off” averaged a 1.1 rating, 3 share in adults 18-49 and 4.1 million viewers overall. 

Note that on average this season, “The Sing-Off” has been adding 20 percent to its next-day “live plus same day” 18-49 rating when Nielsen reports additional time-shifted viewing in “live plus seven day” ratings.
 
At 10 p.m. ET, “Rock Center” averaged a 0.9/2 in 18-49 and 3.4 million viewers overall.

(source; NBC)